1. Field of the Invention
The present invention relates to a combination of two or more powder coatings usable in a powder coating method for forming a coating film having visually homogeneous hue by mixing two or more powder coatings of which each color is different, and to a coating method for forming a coating film having visually homogeneous hue using the above powder coatings.
2. Discussion of the Related Art
Conventionally, powder coatings have been prepared by adding numerous color pigments to resins, curing agents, additives, blending the above components, melt-kneading the mixture, followed by cooling, pulverization, and classification. Also, powder coatings prepared by dry-blending two or more primary colored powder coatings having an average particle size of 10 μm or less for color adjustment, and granulating the obtained powders to a particle size of from 30 to 50 μm have been reported, as disclosed in Japanese Patent Laid-Open No. 7-188586, of which the disclosure is incorporated herein by reference. However, in these powder coatings, the powder coatings have to be prepared for each color needed, so that an enormous number of powder coating products are needed. Similarly, in order to simplify the toning process, as disclosed in Japanese Patent Unexamined Publication No. 4-504431, which corresponds to U.S. Pat. No. 5,319,001, of which the disclosure is incorporated herein by reference, there has been proposed to provide a powder coating prepared by forming a composite of several kinds of colored powders, each of colored powders, having a particle size of preferably 10 μm or less, the composite being granules comprising agglomerates of colored powders and having a particle size of from 15 to 75 μm, whereby the different colors applied during coating cannot be discerned by the human eyes.
However, even if these colored powders were very fine, having a particle size of 10 μm or less, it is actually not easy to form a coating film of visually homogeneous hue depending upon the combination of two or more colored powders. Moreover, those powder coatings need a granulation process or a composite-forming process, thereby making it difficult to prepare powder coatings of desired hue in a simple process.
Also, when a powder coating is used by homogeneously mixing two or more powder coatings having different colors, there are some cases where white pigments are used for giving good covering ability. However, when white pigments are contained in all of the powder coatings blended, the resulting coating film tends to be inferior in chroma.
Accordingly, an object of the present invention is to provide a combination of powder coatings usable in a powder coating method for forming a coating film having visually homogeneous hue by mixing two or more powder coatings of which each color is different.
Another object is to provide a powder coating composition usable in a powder coating method for forming a coating film having visually homogeneous hue, the powder coating composition comprising two or more powder coatings.
A still another object is to provide a coating method using the powder coating of the present invention.
These and other objects of the present invention will be apparent from the following description.